It has been known that various platinum compounds have antitumor activities, and for example, cisplatin (Jap. OPI 49-7224), malonato(1,2-diaminocyclohexane)platinum (II) [Jap. OPI No. 53-31648], and sulfato(1,2-diaminocyclohexane)platinum (II) [Jap. OPI No. 54-44620] have been reported as such compounds.
The present inventors have investigated intensively to find the platinum compounds which have more potent antitumor activity and less toxicity than the prior art compounds, and have accomplished the present invention.